A couple of things.
A very small point, the UK is in Europe, and AFAICR we have had 3-pin plugs, 3-wire cables, since the late 50's.
My house was rewired in the 80's, and we have Earth Leakage Circuit Breakers (ELCB) on every circuit. So even if I stuck a fork into my toaster while grabbing a copper water pipe, I'd expect it to trip (I am not willing to back this up with evidence :-)
When I have visited continental Europe, I am pretty sure that I've seen the same ELCB technology in use.
I suggest that is even more effective than having an Earth connection; after all, if I touched the correct bit of wire in your toaster with my fork, without touching anything else, the Earth connection via a plug would do me no good. Further, unless the device had a metal case connected to Earth, I don't think I am much more likely to touch both Earth and live than just live alone.
I imagine the cost of rewiring all of the houses in Europe which have two-wire cabling t have three-wire would be very large. However, upgrading the distribution panel with ELCB is pretty simple (a drop in replacement in some cases for an old fashioned fused unit), and could be caused to happen more easily when electricity metres need replacing.
AC plugs can be used with adapters. The adapters allow a UK style plug to fit in a US wall socket or a French wall socket and vice versa. You normally see them for sale at airports.
So, get yourself a bunch of adapters to suit the wall socket of your choice then buy a wall socket that is compatible with being soldered to a PCB. If it needs to be a regular wall socket on a flying lead then is this going to be a problem?
Maybe get one of these: -
Retention mechanism: Some sockets have a spring loaded ball like structure (or variant) that engages this hole as a "detent" holding the plug in place.